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Acyclovir

Generic Name: acyclovir (oral) (a SYE klo veer)
Brand Name: Sitavig, Zovirax

Medically reviewed by Sophia Entringer, PharmD. Last updated on Apr 14, 2020.

What is acyclovir?

Acyclovir is an antiviral drug. It slows the growth and spread of the herpes virus in the body. It will not cure herpes, but it can lessen the symptoms of the infection.

Acyclovir is used to treat infections caused by herpes viruses, such as genital herpes, cold sores, shingles, and chickenpox.

Sitavig (acyclovir tablet, delayed release) is only for use in treating cold sores on the lips. Sitavig will not treat genital herpes.

Important Information

Take acyclovir for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.

Treatment with acyclovir should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Herpes infections are contagious and you can infect other people, even while you are being treated with acyclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Before taking this medicine

You should not take this medicine if you are allergic to acyclovir or valacyclovir (Valtrex). You should not take acyclovir buccal tablets (Sitavig) if you are allergic to milk proteins.

To make sure this medicine is safe for you, tell your doctor if you have:

  • kidney disease; or

  • a weak immune system (caused by disease or by using certain medicine).

Tell your doctor if you are pregnant or breastfeeding.

Herpes can be passed to your baby during childbirth if you have a genital lesion when your baby is born. If you have genital herpes, it is very important to prevent herpes lesions during pregnancy. Take your medicine as directed to best control your infection.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

Acyclovir should not be given to a child younger than 2 years old.

How should I take acyclovir?

Take acyclovir exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Start taking acyclovir as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters). Start taking Sitavig within 1 hour after you first notice sold core symptoms, before the cold sore appears.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

Do not crush, chew, suck on, or swallow a buccal tablet. Place the flat side of the tablet against your upper gum, on the same side of the mouth as your cold sore. Allow the tablet to dissolve in your mouth throughout the day. You may eat and drink normally while the buccal tablet is in place.

Do not give an acyclovir buccal tablet to a young child or choking could occur.

Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Acyclovir doses are based on weight (especially in children and teenagers). Your dose needs may change if you gain or lose weight.

Drink plenty of water while you are taking this medicine to keep your kidneys working properly.

Use this medicine for the full prescribed length of time, even if your symptoms quickly improve. Skipping doses may increase the risk of your virus becoming resistant to medication.

Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking acyclovir?

Avoid brushing your teeth, chewing gum, or wearing an upper denture while you have a buccal tablet in your mouth. You may rinse your mouth gently. Drink plenty of liquids to prevent dry mouth.

Herpes infections are contagious and you can infect other people, even while you are being treated with acyclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Taking acyclovir will not prevent you from passing genital herpes to your sexual partner. Avoid sexual intercourse while you have active lesions or the first symptoms of an outbreak. Genital herpes may still be contagious through "viral shedding" from your skin, even if you have no symptoms.

Acyclovir side effects

Get emergency medical help if you have signs of an allergic reaction to acyclovir: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • easy bruising or bleeding, purple or red pinpoint spots under your skin;

  • changes in behavior;

  • confusion, hallucinations; or

  • signs of a kidney problem - little or no urinating; painful or difficult urination; swelling in your feet or ankles; feeling tired or short of breath.

Common acyclovir side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect acyclovir?

Acyclovir can harm your kidneys, especially if you also use certain medicines for infections, cancer, osteoporosis, organ transplant rejection, bowel disorders, or pain or arthritis (including aspirin, Tylenol, Advil, and Aleve).

Other drugs may interact with acyclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use acyclovir only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Frequently Asked Questions